Signaling system for railroads



June 28, 1938. c. s. BUSHNELL SIGNALING SYSTEM FOR RAILROADS Filed Dec. 30, 1.952 2 Sheets-Sheet l INVENTOR 1 6% 6 fiTRNEY v I June 28, 1938.

C. S BUSHNELL SIGNALING SYSTEM FOR RAILROADS Filed Dec. 50, 1932 2 Sheets-Sheet 2 I ATTORNEY Patented June 28, 1938 UNITED STATES ATENT OFFICE Charles S. Bushnell, Rochester, N. Y., assigncr to General Railway Signal Company, Rochester, N. Y.

Application December 30, 1932, Serial No. 649,612

15 Claims.

This invention relates to automatic block signaling systems for railroads and more particularly to a system having a plurality of signal in dications governed according to the character of energy present in the track circuit of each block, as distinguished from a system using line wires between blocks.

In one well known type of automatic block signaling system, the signals are arranged to display a stop or most restrictive indication when a train occupies the associated block, and line circuits are employed to reflectfithis condition back to effect the display of successively lesser restrictive indications at signals located one or more blocks in the rear. Such line circuits are not only costly to construct and maintain but also any failure of these circuits due to broken line wires or crosses between wires will obviously result in improper operation of the signals. Also in such systems, these'linecircuits are often extended parallel to or in a cable with power transmission circuits, and consequently it has been found that the signal line circuits may be falsely energized from current either induced or conducted from the power transmission wires which obviously results in an improper signal indication. The track circuit for effecting the display of a stop or most restrictive indication at its associated signal is usually of' the normally energized type employing a track relay which requires a comparatively low resistance shunt to effect the dropping of its contacts because the characteristics of these relays are such that the current required to effect the dropping of the contacts is of a substantially lesser amount than the current required to pick up the contacts.

In View of the above and other considerations, it is proposed in accordance with the present invention to construct an automatic block signaling system having track circuits which are energized by impulses of a polarity and arrangement selected by forward trafiic conditions to form distinctive codes, and it is proposed to provide means distinctively responsive to each of these codes in a manner to efiect the display of a corresponding signal indication. It is further proposed to increase the reliability of the track circuits governing the display of a stop signal indication by causing such an indication to depend upon the picking up of an associated track relay rather than upon its dropping away.

Other objects, purposes and characteristic features of the present invention will appear as the description therefor progresses, during which references Will be made to the accompanying drawings which show the invention in a manner to make it easily understood, rather than with the idea of showing the particular construction preferably employed in practice, and in which:

Fig. 1 diagrammatically shows an automatic block signaling system arranged in accordance with the present invention for governing trafiic in a single direction over a portion of a railway system. a

Fig. 2 shows a modified form of a block signaling system also in accordance with the present invention. 1

Referring to Fig. l of the accompanying drawings, a portion of a railway system has been shown as divided into blocks or insulated track sections T T T and T and although the signaling apparatus and circuits associated with each of these blocks is substantially identical, it is considered expedient to duplicate this apparatus and circuits at each location in order to disclose the manner in which the system functions to display each indication as transmitted successively to the rear of an occupied block. Inasmuch as identical apparatus is employed at each block, like reference characters will be given to the like apparatus and distinctive exponents will be assigned thereto by which they may be associated with their proper location in thesystem.

A three-position polarized track relay TR (with distinctive exponent) is connected across the rails of each block in the conventional manner, and these relays may be of any suitable type such as the type disclosed in the patent to O. S. Field No. 1,749,331 granted March 4, 1930. A normal slow releasing neutral relay NR (with distinctive exponent), and a reverse slow releasing neutral relay RR (with distinctive exponent) are employed to repeat the relative energized positions of these track relays. The other end of each track section, that is, the end opposite the track relays TR, is energized through contacts of an impulsing relay P (with distinctive exponent) from a suitable source of energy E (with distinctive exponent) which may be a storage cell such as conventionally used in track circuits. This relay P is illustrated as being of the type disclosed in the prior application of O. S. Field Ser. No. 452,666 dated May 15, 1930, and it may be here mentioned that this relay when energized operates an armature about a center pivot point in equally time-spaced oscillations to peto the use of such a relay as other arrangements may be substituted, such as two neutral relays having their energizing circuits interlocked to produce alternate operation.

A signal S (with distinctive preceding numeral) is shown as governing trafiic in a single direction over each of the above mentioned track sections T (with distinctive exponents), and although these signals have been illustrated as being of the individual color light type, it is understood that any other type of signal may be employed and controlled in'a manner obvious from the following description. A control circuit for each signal light of the signals S is shown in detail, and it is understood these are the lights or the incandescent lamps associated with the corresponding unit of the signals S shown at the en trance of each block or track section. The upper lights G, Y and R (with distinctive preceding characters by which they may be associated with the corresponding signal S) may be the conventional three indication signal while the lower lights AG and AR (also having distinctive. preceding characters) are employed to modify or determine the degree of restriction of the upper caution signal light Y, but the lower red light AR is always displayed in combination with either the upper green light G or the upper red light R. In this arrangement the four signal aspects may be arranged in their relative degrees of restriction as a green over a red light for a proceed indication, a yellow over a green'light for a proceed-caution indication, a yellow over a red light for a restricted caution indication, and a red over a red light for a stop indication.

Having thus described the various apparatus associated with Fig. 1, it is believed that the function of the system to display the various signal indications will be more readily understood by assuming a particular traflic condition and describing the operation of the apparatus resulting therefrom, or that is, it will be considered that a train represented by the symbol A is occupying the track section T The train A is then effective to shunt the track circuit current from the track relay TR thereby causing its contact 5 to assume a de-energized position as shown, which in turn is effective to de-energize the slow acting relays RR and NR A stop indication is then displayed at the signal IS by energizing the red signal lamp ISR over a circuit including back contact 5 of relay NR and back contact 6 of relay RR and the red signal lamp ISAR is also energized over a circuit including back contact 1 of relay NR and back contact 8 of relay RR It was previously mentioned that the impulsing relay P will continuously operate in the form shown in Fig. 1 in equally time-spaced oscillations, which operation may be briefly described by referring to relay P which relay, when in the condition shown, has a circuit completed for energizing its right hand operating coil from over wire 9, through its right hand operating coil, wires in and l I, through its contact H2 in the position shown, and wire l3 to This circuit is then obviously effective by shunting the left hand coil to cause the right hand coil to operate the armature I 2 to its dotted position, which then obviously shunts the right hand coil and causes the left hand coil to attract the armature l2 back to the position shown. This operation continues to cause periodic and alternate oscillations of the contacts operated by the relays P. It may also be mentioned that the contacts of the relays P are so arranged that during operation any particular set of contacts is being closed at substantially the same time as the opposite set of contacts is being broken, or in other words, a negligible period of time exists in which neither set of contacts is closed.

With the impulsing relay P in the position shown the track section T is energized with current of a definite polarity, over a circuit from the terminal of battery B back contact 14 of relay NR back contact [5 of relay RR contact l6 of relay P wires I1 and I8, through the lower rail of the track section T wire l9, through the operating winding of relay TR wire 2?], through the upper rail of the track section T wire 2!, contact 22 of relay P back to the terminal of battery B However, when the relay P operates to open contacts I6 and 22 and close contacts 23 and 24, the track section T is deenergized for the reason that the circuit to battery B is open at the parallel front contacts 25 of relay RB and 26 of relay NR It is then obvious that with the relays RR and NR both de-energized the relay P is effective to apply impulses of a definite polarity (which may be termed impulses) to the track section T which impulses are separated by periods of deenergization which are substantially of the same duration of time.

These time-spaced impulses applied to the track section T are effective to operate contact 21 of relay TR. alternately from its right hand position as shown to its de-energized or dotted position in synchronism with the operation of the impulsing relay P and during the period in which the contact 2i is swung to its right hand position, or during the energized period of the track section T an obvious circuit is completed to pick up the slow releasing relay NR However, the characteristics of this relay NR are r such that it does not drop-away during the period in which the contact 2! assumes its deenergized or dotted position, and consequently remains picked up as long as the impulses continue. With the relay NR picked up and the relay RR de-energized a circuit is completed for energizing the yellow or caution signal light 2SY at front contact 28 of relay NR and back contact 29 of relay RR and the red signal light ZSAR is also energized over a circuit including front contact 30 of relay NR, thereby displaying a restricted-caution indication at signal 28.

With this condition existing at the signal 28, the track T is energized with time-spaced impulses in a similar manner to the track section T but these impulses are of the reverse polarity (which may be termed impulses) applied thereto from battery B over a circuit completed at front contact 3! at relay NR and through contacts of the relay P, It is not considered necessary to trace this circuit in detail by reason of its similarity to the circuit traced in describing the energization of the track section T but it is obvious that the closing of front contact 3| of relay NR connects the positive terminal of the battery B through the right hand set of contacts of the relay P to the upper rail instead of through the left hand set of contacts as in the relay P to the lower rail thereby causing the current flowing in the track section T to be in the opposite direction to that flowing in the track section T It was previously considered that current flowing from left to right through relay TR. operated its contact 21 to the right, and consequently the reverse direction of current, or current flowing from right to left through relay TR operates its contact 32 to the left. These timespaced impulses of the track section T are obviously effective to oscillate the contact 32 of relay TR from its left hand position as shown to its de-energized or dotted position in synchronism with the operation of relay 1? thus causing the relay RR to be picked up and the relay NR to be dropped, which is the reverse of the condition set up by the relay TR A circuit is thus completed to energize the yellow or caution signal light SSY through back contact 33 of relay NR and front contact 3% of relay RR and the green signal light 3SAG is energized over a circuit completed at back contact 33 of relay NR and front contact 35 of relay RR thereby displaying a proceed-caution indication at signal 38 which is of a lesser restriction than displayed by signal 23 by reason of the energization of the green signal ZSAG.

With this condition existing at the signal 38, the track section T is energized with impulsesof a polarity such as applied to the track section T which are separated or which alternate with impulses of a polarity such as applied to the track section T or that is, the energization of section T is made up of alternating and impulses. This energization is obviously effected by the fact that the terminal of battery B is connected to both the left hand set of contacts of the relay P by front contact 36 of relay RR as well as to the right hand set of contacts by the front contact 31 of relay RR With these impulses of alternating polarity applied to the track section T it is obvious that the relay TR; will operate its contact 38 from its extreme left hand position to its extreme right hand position I in synchronism with the operation of the relay P thereby effecting the picking up of both relays RR and NR The green signal light 48G is then energized over a circuit including front contact 39 of relay NR and front contact 5B of relay RR, and the red signal QSAR is energized over a circuit including front contact 4! of relay NR to thereby display a green or proceed indication at signal 4S. The track section at the left of section T is likewise energized with impulses of alternating polarity inasmuch as the relay BB is energized to connect the positive terminal of battery 33 to both the right hand and the left hand sets of contacts of the relay P and consequently a signal at the left or in the rear of signal 43 will likewise display a green or proceed indication.

It is evident from the foregoing description of the operation of the system shown in Fig. 1 that a train occupying any one of the insulated track sections T is effective to shunt the associated polarized track relay TR thereby dropping both slow-releasing relays RR and RN which effects the display of the most restrictive signal indication at the entrance of that occupied section. These relays RR and RN are also effective in combination with the associated impulsing relay to apply a distinctively coded impulsing energization to the rear adjacent section which in the form shown comprises time-spaced impulses of a particular polarity, which for comparison is lay from one extreme position to center which picks up only one of the slow releasing relays, namely relay NR, which effects the display of the next lesser restrictive indication with respect to that displayed at the entrance of the occupied section, or that is, a yellow high light limited by a red lower light. With the NR relay only picked up, an impulsing energization is applied to the section in the rear'thereof, that is the second section in the rear of the occupied section, which energization comprises time-spaced impulses of the opposite polarity, termed polarity.

These time-spaced impulses are eifective in a similar manner to oscillate the contact of the associated track relay thereby picking up the other slow releasing relay only, namely relay RR, which effects the display of a signal indication at the entrance of the second section in the rear of the occupied section which is of lesser restriction than displayed at the section adjacent the occupied section, or that is, a yellow high light modified by a green lower light. Whenever this relay RR is picked up at any section, an impulsing energization of alternating and polarities is applied to the rear adjacent section.

The third section in the rear of the occupied section is consequently energized with current of alternating and polarities which oscillates the contact of the associated track relay in a manner to pick up both slow-releasing relays NR and RR thus efiecting the display of the least restrictive signal indication. In a like manner this 'least restrictive indicationis rethe RR relays are picked. up to effect the application of impulses of alternating polarities to their respective rear adjacent sections.

In Fig. 2, a modified arrangement of the pressections, but theimpulsing of the energization of any particular track section and the display of the various indications associated therewith is only effected when a train is approaching that section, thereby obviously saving unnecessary consumption of energy by the signal lights as well as unnecessary operation of both the impulsing means and the code-responsive means. In order to prepare the system for displaying signal indications to an approaching train. a polarized line circuit is employed which interconnects the adjacent track sections, and this line circuit is selectively energized from suitable split-potential batteries at each section, which batteries have been omitted fromthe drawings, but it is understood that and are opposite extreme terminals and (c) is the center or common potential thereof. A common line wire is. necessary in addition to the line wires shown as connecting the track sections, which common wire has also been omitted but it is understood that it will be connected to the center tap or common of each split potential battery and to each of the terminals marked c) in the drawings.

Additional apparatus is required in the form shown in Fig. 2 which apparatus comprises polarized line relays L (with distinctive exponents) which may be of the same type as the polarized track relays TR, slow releasing relays DR (with distinctive exponents) which repeat the de-energized position of the track relay TR, and relays G (With distinctive exponents) which prevent the flashing of the green signal light when the restriction of the yellow indication is changing as will be more fully described later.

It is to be understood that the apparatus and circuits associated with each track section of the system is identical and before describing the operation of the system to prepare for an approaching train, the effect of a train occupying a particular track section will be described.

For example, if a train enters the track section T of Fig. 2, the track circuit current will be shunted from the track relay TR thereby causing its contact 56 to assume its de-energized or center position which then effects the de-energization of both relays RR and NR With the relays RR and NR de-energized, current of a definite polarity will be applied over the line circuit to the polarized line relay associated with the forward adjacent track section, or in the present case, relay L". This circuit for energizing the relay L may be traced from the common wire or the centered tap (c) of the associated line battery, through the windings of the relay L over line wire 47, back contact 48 of relay NR wire 49, back contact 50 of relay RR to of the same line battery. Current flowing in this direction through the line relay L, or namely from right to left, will cause the polarized contacts thereof to swing to their extreme left hand position and inasmuch as the system is symmetrically arranged it will be considered that this operation of any line relay L will occur whenever a train occupies the rear adjacent track section.

In considering the operation of the system in preparation for an approaching train, it will be considered that the apparatus shown in Fig. 2 is all assuming the definite position shown, and it will be considered that a train represented by the symbol A is occupying the track section T This train A then effects the energization of the line relay L which is associated with the forward adjacent track section T to operate its contacts to the left as shown, all of which will be obvious from the foregoing description of the energization of the similar relay L' during the occupancy of the track section T With the line relay L energized to swing its contacts to the left, the line relay L is energized with a polarity which is the reverse of the energization of relay L over a circuit from of the associated line battery, through front contact 5! of relay L polar contact 52 of the same relay, wires 53 and 55, front contact 48 of relay NR line wire 41 through relay L" to the common wire (0) or common potential of the same line battery. This reverse polarity of energization of the relay L or that is, with current flowing from left to right through its windings, operates its polarized contacts to the extreme right hand position thereby opening one energizing circuit for next forward line relay L at the polar contact 55, and

, inasmuch as the relay ER is picked up in response to a clear traffic condition, the circuit for applying the reverse polarity thereto is also opened at back contact 45 of relay RE".

From the above description of the line circuits of Fig. 2, it may be seen that a train entering any track section is effective to energize the line relay associated with the first forward section with a definite polarity which operates the polarized contacts of this line relay to a position which applies energy of an opposite polarity to the line relay associated with the second forward section, but this operates the polarized contacts of this sec- 0nd line relay to a position which does not energize the line relay associated with the third for.- ward section. This operation of the line circuits obviously shifts from section to section in advance of the train as it progresses throughout the system, and with such operation in mind, the means for initiating operation of the impulsing means and energization of the signal lamps will now be considered.

The energization applied to the line relay associated with the second section in advance of the occupied section, or relay L is effective to pick up the neutral contacts thereof although the polarity of such energization operates the polar ized contacts to a position having the same effect on the circuits which they control as during the de-energized condition of the relay. The neutral front contact 44 of relay L then energizes the impulsing relay P and the rails of the rear adjacent section T are connected to the oscillating contacts of the relay P by the respective neutral front contacts 56 and 51 of relay L". The associated track battery B is then connected to the contacts of relay P" to apply impulses of energy to the section T of a polarity and arrangement selected by the positions of relays RR and NR", all of which is accomplished in the same manner as described in connection with the embodiment shown in Fig. 1 and consequently will not be described in detail. However, considering that the same code arrangement as used in Fig. 1 is employed, a code comprising alternating and impulses is transmitted over the section T which distinctly affects the code receiving means at the entrance of this section also in the same manner as described in Fig. 1 inasmuch as the same code receiving means is employed with the exception of the added relays G and DR which do not function in this case.

With the line relay L energized with a normal polarity as previously described, the code receiving means is now effective to energize the clear signal light GSG over a circuit from front contact 58 of relay RR front contact 59 of relay NR back contact 60 of relay G through the signal light GSG, polar contact 6| of relay L in its left hand position, neutral front contact 62 of the same relay to The lower red signal light SSAR is likewise energized over an obvious circuit completed at front contact 63 of relay NR thereby displaying a clear or green over red indication at signal 68 to the approaching train A However, no indication is displayed at the signal associated with second section in advance of the train A or considering section T the polarized contact 64 of relay L being in its extreme right hand position opens the energizing circuit for all the signal lamps at signal is, and likewise no indication is displayed at succeeding forward sections, or as may be seen at section T the energizing circuit for all the signal lamps at signal 88 is opened at the neutral front contact 65 of relay L which is de-energized.

The circuit for energizing the track section T with the relay L de-energized is shifted to exclude the contacts of the impulsing relay P and this relay P is de-energized by the open front contact 12. The track section T" is then energized with continuous current over a circuit from the terminal of battery 3*, front contact 6'! of relay RR back contact 58 of relay L through the upper rail of the track section T through the windings of relay TR from right to left, through the lower rail of section T back contact 69 of relay L front contact 10 of relay RR", to the side of battery B This continuous current flowing through'relay TR from right to left causes its polarized contacts to operate to their extreme left hand position thereby maintaining relay RR' energized.

It is then obvious that when a train is not approaching or if approaching and more than one section in the rear of any particular section of the system shown in Fig. 2, the energization of that particular section is continuous rather than impulsing, and of a polarity which corresponds to the forward trafiic conditions, or as may be seen by considering the energization of section T the polarity is selected by contacts 66 and II of relay NR and contacts 61 and 10 of relay RR This means for selecting the polarity of continuous energization of a section which is not being approached by a train may be more' clearly understood by considering that the section T is occupied thereby shunting relay TR and dropping both relays BB and NR. This condition reverses the energization of section T by the pole-changing contacts 61 and E of relay BB de-energized, which contacts are connected to the rails or the section T through back contacts 68 and 69 of relay L de-energized, which circuit is considered to be obvious from the drawings and foregoing description and will not be traced in detail. This reversed polarity shifts the polarized contacts of relay TR to the right hand position picking up relay NR and dropping relay RR but a caution indication is not displayed at singal is until an approaching train energizes the relay P to impulse this energization and oscillate contact 43 of relay 'I'R' from the right hand position to center thereby picking up both relays NR and DR. A circuit is then completed for energizing the caution signal light TSY including front contact 15 of relay DR", front contact 16 of relay NR' and back contact TI of relay RR and the lower red light 'ISAR is energized over a circuit completed at front contact 18 of relay NR The chief function of the DR relays, which are energized when the associated track relay is deenergized or oscillating from one extreme position to center, is to control the signal energizing circuits in a manner to display a most restricted indication in the event that an approaching train fails to impulse the energization of the associated track section due to a failure of a line circuit or an impulsing relay. This may be specifically pointed out by considering that a train isapproaching the section T, but for some reason either the impulsing relay P fails to operate or the line relay L fails to connect the rails to the contacts of the impulsing relay thus substituting a caution or a Y indication for what should be a clear or G indication, were it not for the DR." relay. In this case the energization of the section T' is continuous which picks up either relay ER or NR according to the polarity but does not pick up relay DR A circuit is then completed, due to the DR relay, for energizing the red signal light TSR including back contact 19 of relay DR and either back contact 80 of relay NR. or back contact 8| of relay RR' and the lower red light ISAR is also energized over a similar energizing circuit obvious from the drawings. Thus a failure of the clear indication, G, instead of giving a caution indication, Y, gives a stop indication, R, so as to apprise the train man that the signal system is out of order.

The specific function of the G relays in Fig. 2

may be described by considering the signal 2S of Fig. 1 during a condition in which its indication is changing from the yellow over red indication as shown to a yellow over green indication now shown as displayed by signal 38. In changing this indication at signal 23, the relay BB must be picked up and the relay NR dropped, but as the pick-up time of these relays must be shorter than the drop-away time, there will be a period of time in which both relays will be picked up and obviously energize the green signal light 23G during such period. To obviate such a flashing of the green signal light, the relays G were added in the embodiment shown in Fig. 2 and arranged to be picked up whenever either of the slow-releasing relays NR or RR is de-energized and to control the ener gizing circuit for the green signal lights through a back contact thereof. This arrangement in Fig. 2 obviously requires the relay G to drop when both relays NR and RR are picked up before the green signal light can be energized, and the drop-away time of the relay G is arranged to be greater than the time required for the execution of the change in condition of the slow releasing relays, thus holding the energizing circuit for the green signal light open during a change in the yellow. indication.

An automatic block signaling system has thus been provided in which an indication of any one of four different .degrees of restriction is automatically displayed at the entrance of each block or section of the system, and in which such various indications are selectively displayed without the use of auxiliary line circuits inter connecting the blocks. A modified form of such a system has also been provided which enables the saving of considerable energy and needless operation of various parts by preventing the display of a signal indication and stopping the oscillating operation of certain apparatus at times when a train is not approaching or occupying the section with which the particular signal and apparatus are associated.

A further feature which is inherent in the present invention is the increased reliability of the operation of the track circuits. This is bcause the impulsing energization of the track circuits effects the alternate picking up and dropping of the track relays, and inasmuch as it is well known that a larger amount of current is required to pick up than is required to hold up such relays, it follows that more reliable shunting of the track circuits will be obtained by enabling a higher resistance rail shunt to prevent picking up of the oscillating track relay than would effect the dropping of a continuously energized relay.

The above rather specific description of one form of the present invention is given solely by the way of example, and is not intended, in any manner whatsoever, in a limiting sense. It is also to be understood that various modifications, adaptations and alterations may be ap plied to meet the requirements of practice, with out in any manner departing from the spirit or scope of the present invention, except as limited by the appended claims.

Having thus described my invention, what I claim is:-

1. In a railway signaling system, a plurality of insulated track sections, a polarized relay connected across one end of each track section, two slow releasing relays controlled by each polarized relay in a manner to distinctively respond to variously coded impulses applied to the asso ciated track section, a signal associated with each track section, control means efiecting the display of indications at each of said signals in accordance with the condition of the associated slow'releasing relays, an oscillating contact means connected to the other end of each track section, a source of energy associatedwith each track section, and means for selectively connecting each source of energy to the contacts'oi the associated oscillating contact means in a manner to form said variously coded impulses in accordance with the position of the slow releasing relays associated with one adjacent track section.

2. In a railway signaling system, an insulated track section, a forward adjacent track section and a rear adjacent track section, means for selectively applying impulses of one polarity, of a different polarity or of alternating polarities to one end of said insulated track section in accordance with the trafiic condition of said forward track section, a polarized relay connected to the other end of said insulated track section and responsive to each of said impulses applied to the track section, signal control relays selectively energized by the polarized relay, and means for selectively applying impulses of one polarity, of a difierent polarity or of alternating polarities to said rear adjacent track section in accordance with the condition of said signal control relays.

3. In a railway signaling system, an insulated track section with at least three forward track sections and a rear adjacent track section, a first source of direct current energy, a means for applying impulses generated from said first source of energy to one end of said insulated track section which are selected by differing polarity and sequence to form any one of three distinctive codes in accordance with the location of a train in said three forward track sections, a signal control means connected to the other end of said insulated track section which signal control is distinctively responsive to said distinctive codes, a second source of direct current energy, and a means for applying impulses generated from said second source of energy to said rear adjacent track section which are distinctively coded in accordance with the condition of said signal control means.

4. In a railway signaling system, a plurality of insulated track sections, a wayside signal associated with each section, signal control means for each section for effecting the display of a most restrictive indication at said signals when a train occupies the associated section, means including the signal control means arranged to apply time-spaced impulses of one polarity to the first section in the rear of a section occupied by a train, means including the signal control means arranged to apply time-spaced impulses of another polarity to the second section in the rear of a section occupied by a train, the signal control means at each section being arranged to distinctively respond to each of said time-spaced impulses, and means including the signal control means arranged to apply impulses of alternating polarities to the third section in the rear of a section occupied by a train, whereby said signal control means distinctly responds to each of said impulses of alternating polarities.

5. In a railway signaling system, a plurality of track sections, means normally energizing each of said sections with continuous current, means for impulsing the continuous current of said sections upon the approach of a train, code selecting means at each section arranged to select the polarity and-arrangement of said impulsing energy to form any one of three distinctive codes in accordance with forward traflic conditions, and code responsive means at each section operable to distinctively respond to the coded impulses of the associated section.

6. In a railway signaling system, a plurality of track sections, means normally energizing each of said sections with continuous current, means for impulsing the continuous current of said sections upon the approach of a train, code selecting means at each section arranged to select the polarity and arrangement of said impulsing energy to form any one of three distinctive codes in accordance with forward traffic conditions, code responsive means at each section operable to distinctively respond to the coded impulses of the associated section, wayside signals at each section arranged to display various indications to an approaching train in accordance with the condition of the associated code responsive means, and means for preventing the display of signal indications when a train is not approaching the associated section.

'7. In a railway signaling system, two adjacent insulated track sections, an oscillating contact means operable to actuate contacts in substantially equal time-spaced oscillations, a source of energy, two slow releasing relays having code selecting contacts arranged to connect said source of energy through said oscillating contacts to one end of one of said track sections whereby timespaced impulses of either one polarity or of another polarity or impulses of alternating polarities are selectively applied thereto, a polarized relay connected to one end of the other track section and responsive to code impulses, one of the slow-releasing relays being picked up during one polarity of impulsing energization of said polarized relay, and the other slow-releasing relay being picked up during another polarity of impulsing energization of said polarized relay, the slow-releasing relays being arranged to both pick up during alternate polarities of energization of said polarized relay.

8. In a railway signaling system including a plurality of track sections each selectively energized by impulses coded in accordance with the respective forward trafiic conditions, a polarized relay at each track section arranged to distinctly respond to said coded impulses, two slow releasing relays associated with each of said polarized relays and connected in a manner to select various circuits in accordance with the coded impulses applied to the associated polarized relay, signal means arranged to display a clear or any one of a plurality of more restrictive indications in accordance with the circuit selected by the associated slow releasing relays, and means for preventing a momentary display of a clear indication on changing from one to another of the more restrictive indications.

9. In a railway signaling system, a plurality of track sections, energizing means for each track section, wayside signals associated with each track section, a polarized line relay associated with each track section, a circuit for energizing said line relay with current of one polarity when a train occupies a rear adjacent track section and with current of another polarity when a train occupies a second rear track section, means effective when said line relay is energized with ourrent of either polarity to impulse the energization of the track section next in the rear, and means permitting said signals to display an indication only When the associated line relay is en ergized with current of one polarity.

10. In a railway signaling system, a plurality of track sections, energizing means for each track section, wayside signals associated with each track section, a polarized line relay associated with each track section, a circuit for energizing said line relay with current of one polarity when a train occupies a rear adjacent track section and With current of another polarity when a train occupies a second rear track section, means effective when said line relay is energized with current of either polarity to impulse the energization of the track section next in the rear, means permitting said signals to display an indication only When the associated line relay is energized with current of one polarity, and means effecting the display of a most restrictive indication at said signals when the associated line relay is energized with current of said one polarity but the energization of the associated track section is not impulsing.

11. In a railway signaling system, a first track section, a rear and a forward track section adjacent thereto, a polarized line relay associated with each of said track sections, a wayside signal associated with each of said track sections, a circuit arranged to apply one polarity of energy to the line relay associated with said first track section when a train occupies said rear adjacent track section, a circuit arranged to apply another polarity of energy to the line relay associated with said forward adjacent track section when the line relay associate-d with said first track section is energized with said one polarity, means for applying coded impulses to each of said track sections when the line relay associated with the section next in advance is energized with either of said polarities, and means for displaying a signal indication by said wayside signals only when the associated line relay is energized with said one polarity.

12. In a railway signaling system, a plurality of track sections, a polarized relay connected across one end of each track section, two slow releasing signal control relays controlled by each of the polarized relays, a continuous current source of energy, and means for selectively applying interrupted current from the source of energy of one polarity, a different polarity or of alternating polarities to the other end of each track section in accordance with the energization of the associated signal control relays, said current being interrupted at a frequency whereby the associated polar relay can operate substantially in synchronism therewith.

13. In a railway signaling system, a plurality of insulated track sections, means for each section for applying time-spaced impulses of one polarity toits track section during a first traific condition, for applying time-spaced impulses of another polarity to its track section during a second trafiic condition, for applying impulses of alternating polarities to its track section during a third trafiic condition, each means including wayside oscillating means distinctively responsive to each impulse applied by the means of the track section next in advance thereof and connected to its track circuit whereby to distinctively respond to each of said arrangements of impulses applied by the means next in advance in a mannercto selectively display various signal indications.

14. In a railway signaling system, a plurality of insulated track sections, means for each section i or generating time-spaced impulses of one polarity in its track section during a first trafiic condition, for generating time-spaced impulses of another polarity in its track section during a second traffic condition, for generating impulses of alternating polarities in its track section during a third trailic condition, and wayside means included in the generating means, connected to its track section which distinctively respond to each of said arrangements of generated impulses generated by the means of the track section next in advance in a manner to selectively display various signal indications.

15. In a coded track circuit system for railroads; a plurality of track circuit sections; a coding device for each track circuit section for controlling the supply of coded rail current to the rails at the exit end of that section; approach control relay means at the exit end of each section and operable over a traffic controlled line circuit by a current of any one of a predetermined number of distinctive characters including a current of a last distinctive character; means controlled by each except the last of said control relay means, when energized by current except current of the last of the distinctive characters, for controlling the supply of current to the approach control relay means for the track section next in advance; each control relay means when energized by current of one of said distinctive characters, except when energized by current of said last character, operating to energize the next control relay means by current of a different distinctive character; and means governed by each of said control relay means when energized for controlling the operation of the associated coding devices; whereby said coding devices are normally inactive while no train is present in said plurality of track sections and are automatically set into operation for a predetermined number of track sections ahead of an occupied track section.

CHARLES S. BUSHNELL. 

